A photo, chart, or recording can explain an idea faster than a paragraph, but only if people can actually use it.
What You Need to Know
Preload can tell the browser an important image will be needed soon. For responsive pictures, imagesrcset and imagesizes help the preload choose a candidate that fits the viewport.
Try the Example
Take a look at the example. We’ll explain the important lines right below it.
<link rel="preload" as="image" href="images/hero-800.jpg"
imagesrcset="images/hero-480.jpg 480w, images/hero-800.jpg 800w"
imagesizes="100vw">
<img src="images/hero-800.jpg" srcset="images/hero-480.jpg 480w, images/hero-800.jpg 800w"
sizes="100vw" alt="A classroom project" width="800" height="450">Let’s Read the Code
- srcset: Srcset offers image candidates for different displays or layout sizes.
- src: Src identifies a resource path for images, frames, or media.
- <link>: Link connects the document to metadata relationships or resources; it is not a visible anchor.
- <img>: The img displays a picture; its alt is the text alternative.
Read the named elements and attributes together. They explain how the browser connects this feature to the rest of the page.
What Happens in the Browser?
The paths shown here refer to files in your own example project. Put real images and recordings in those locations before expecting them to load.
Which picture loads? With width descriptors, sizes describes the expected display width and srcset offers candidates. The browser can also consider screen density and network conditions. Inspect the selected source instead of assuming every screen receives the same file.
Your Turn
Resize the viewport and inspect the chosen image source in Developer Tools. Do not assume the browser always downloads the smallest file.
Common Beginner Mistakes
- Leaving out real media files or understandable text alternatives.
- Always check keyboard access, readable alternatives, and any missing files; a perfect player layout does not guarantee accessible content.
Key Takeaways
- Preload can tell the browser an important image will be needed soon.
- srcset: Srcset offers image candidates for different displays or layout sizes.
- If the resource cannot load, users still need enough text to understand what was meant to be there.